1. Field of the Invention
The invention relates in general to an organic light emitting diode (OLED) display and luminance compensating method thereof, and more particularly to an OLED display, which utilizes the operational current of a dummy OLED to simulate the change of the real pixel current, and luminance compensating method thereof.
2. Description of the Related Art
FIG. 1 is a block diagram showing a circuit structure of a conventional OLED display. The OLED display 100 includes a data driver 110, a pixel matrix 120 and a scan driver 130. The pixel matrix 120 includes several red pixels (R_Pixels) 122, several green pixels (G_Pixels) 124 and several blue pixels (B_Pixels) 126, each of which includes an OLED (not shown in the figure). The data driver 110 includes a horizontal shift register 112, a plurality of red digital/analog current converters R_DACs 114, a plurality of green digital/analog current converters G_DACs 116, and a plurality of blue digital/analog current converters B_DACs 118.
The R_DAC 114, G_DAC 116 and B_DAC 118 respectively receive the digital data R_Data, G_Data and B_Data from the horizontal shift register 112 and convert them into analog currents IR, IG and IB according to a reference voltage Vbias. These analog currents IR, IG and IB are respectively sampled and held by a red sample/hold unit (R_S/H) 115, a green sample/hold unit G_S/H 117 and a blue sample/hold unit B_S/H 119, and then data currents IDR, IDG and IDB are thus generated and outputted to the R_Pixel 122, G_Pixel 124 and B_Pixel 126. The scan driver 130 turns on control switches (not shown in the figure) contained in each row of the pixels 122, 124 and 126 in the pixel matrix 120 in a row-by-row manner such that the OLEDs in each row of the pixels 122, 124 and 126 emit light.
Because the luminance efficiency of the OLED attenuates with the usage time and the luminance attenuation degrees of the red, green and blue pixels are different, the OLED display usually cannot display the correct picture frames after a period of time.